Circuits are being integrated more and more into chemical analysis systems. For these applications there is a need to deliver liquids from external sources into integrated silicon microcircuit sensors. Such a microcircuit may combine electrical components, sensor components and liquid channels to deliver fluids to specific sensors either for testing and electronic recording or to eject samples into a microanalysis plate. Sometimes it is desirable for tens, hundreds, or even thousands of different liquid formulations to be delivered into such a microcircuit. Applications may include for example, microanalysis of chemicals, analysis of body fluids, sequencing of DNA and nucleotides and other medical applications.
In addition, as integrated circuits continue to scale circuit density and power density increases. This necessitates the development of ways to efficiently remove heat from integrated circuits. One such way is to build micro channels into the integrated circuit through which coolant may be pumped.
When stacking multiple chips in a multichip module it may be desirable to run signals from an upper chip to a lower chip. Large through silicon vias may be formed to provide channels through which to run wires from an upper chip to a lower chip.
One method of forming microchannels is to use laser drilling which limits the number of microchannels that may be formed because they are drilled one at a time. A second method is to use deep reactive ion etching (DRIE) which may be very time intensive especially if large diameter microchannels are to be formed. A third method is to use wet etching with an etchant such as tetramethylammoniumhydroxide (TMAH) for example, which typically forms microchannels with highly sloped (about 55% slope) sidewalls due to accelerated etching along silicon crystal planes. A fourth method is to use grit blasting which is not as precise and is not as clean as the methods previously mentioned. With some of the above mentioned methods, simultaneously forming microchannels with different sizes may be problematic because of differences in etch rates vs microchannel size.